Interleukin-1 is a central mediator of chronic inflammatory diseases such as periodontitis. IL-1 binding to its receptor activates a protein serine-threonine kinase, but the mechanism of signal transduction is not completely known. Studies on the effect of IL-1 on gingival fibroblast extracellular matrix metabolism reveal that the magnitude of the response is correlated with the composition and structure of the extracellular matrix (ECM) and the shape of the cells. Receptor binding of radiolabeled IL-1beta shows that IL-1 receptors on gingival fibroblasts are located at focal adhesions, connections between fibronectin in the ECM and the cytoskeleton. IL-1beta/IL-l receptor binding causes a rapid increase in phosphorylation of talin, a transmembrane linkage protein, and alterations in actin filaments and cell attachment. The correlation of the magnitude of the IL-1 effect with cytoskeletal organization and the ECM, indicates that cell shape and cell-matrix interaction may play a role in modulating the response. Thus, the initial alterations induced in the cytoskeleton and cell attachment, could constitute a signal modulating event, causing changes in IL-1 regulated genes following cytoskeletal reorganization. Our pilot study shows a direct correlation between the concentration of fibronectin cells attach to, and the magnitude of the IL-1beta effect on proteoglycan synthesis. Experiments described in the present proposal are designed to determine how cell attachment and cytoskeleton modulate IL-1 effects. Initially, we will determine whether the ECM and its receptors affect binding of IL-1beta to its receptor, or have an effect on the IL-1 activated kinase. Further, we will determine whether changes in the cytoskeleton and cell attachment have an impact on IL-1beta induced biological responses. Subsequently we will analyze the early changes at focal adhesions and in the cytoskeleton induced by IL-1beta binding. Finally we will correlate the effect of the ECM on these early changes with its effect on later IL-1 mediated biological events. The studies will include cell binding assays and plate binding experiments to determine protein-protein interactions. We will assay for IL-1 induced kinase activation by using a peptide from the EGF receptor. Changes in attachment and cytoskeleton will be induced by blocking interactions by specific antibodies or chemicals. These studies will clarify how IL-1 regulation of fibroblast metabolism is affected by the ECM and increase our understanding about how IL-1 modulates cell functions and perpetuates degradation of connective tissues of the gingiva and periodontium.